The present invention relates generally to air or gas sealing arrangements for rotary drums such as high-temperature rotary kilns and, more particularly, to a flexible seal for sealing the opening between a rotating drum and a stationary hood to prevent the ingress and egress of gaseous fluids at the ends of the rotary drum.
It is well known to provide a flexible seal at both ends of a rotary kiln to seal the annular space between the rotating cylinder of the kiln and the stationary housing at each end of the kiln. It is desirable to seal the spaces between the kiln ends and the hoods due to the high temperatures within kilns, which in the case of cement kilns are about 2750.degree. F. to 3000.degree. F. Sealing these spaces provides substantial benefits by confining toxic gases within the kiln and increasing energy efficiency through prevention of loss of the heated gas.
U.S. Pat. No. 4,405,137 describes a flexible rotary seal which uses discrete metal leaves formed from resilient sheet metal which are overlapped and secured to the hood at one end and have the other end secured to a wear liner. The metal leaves are bent and stressed so that the wear liner is biased into continuous engagement with the rotary kiln, and a cable assists in holding the wear liner against the rotary kiln.
While metal leaf rotary seals of the type in U.S. Pat. No. 4,405,137 have proven to efficiently seal rotary kilns, small gaps or spaces may develop between the overlapping metal leaves in operation, particularly if the wear liner wears unevenly. Uneven wear may result if the kiln rotates irregularly or if thermal expansion causes the kiln to develop an irregular shape. It should be noted that for large kilns of several hundred feet longitudinal thermal expansion may be around one foot.
In accordance with the present invention, a rotary seal assembly for rotary drums is provided which incorporates overlapping metal leaves but which provides a greatly reduced tendency to form small gaps or spaces between adjacent metal leaves as the drum rotates, thereby reducing energy consumption and harmful environmental effects.